Commit fcbbcf49 authored by Darek Stojaczyk's avatar Darek Stojaczyk Committed by Ben Walker
Browse files

bdev: cleanup child iov rewind code 



When we run out of bdev_io's child iovs and we had
to round down I/O size to nearest block size boundary,
we used to decrease the existing child_iovcnt and
set a new "child_iov_run_out" flag to terminate the
uppermost splitting loop.

We can get rid of that new flag by just not decreasing
child_iovcnt when rewinding the last few iovs - it
will make the uppermost loop naturally terminate using
the existing checks.

Change-Id: Ie40c7ce135e7fb8fe284afdf7beeebd10af85cb7
Signed-off-by: default avatarDarek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/459911


Reviewed-by: default avatarShuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>
Reviewed-by: default avatarBen Walker <benjamin.walker@intel.com>
Tested-by: default avatarSPDK CI Jenkins <sys_sgci@intel.com>
parent 59262366

lib/bdev/bdev.c

+8 −11
Original line number Diff line number Diff line
@@ -1601,7 +1601,6 @@ _spdk_bdev_io_split(void *_bdev_io) 
	uint64_t parent_iov_offset, iov_len;

	uint32_t parent_iovpos, parent_iovcnt, child_iovcnt, iovcnt;

	void *md_buf = NULL;

	bool child_iov_run_out = false;

	int rc;



	remaining = bdev_io->u.bdev.split_remaining_num_blocks;
@@ -1657,16 +1656,19 @@ _spdk_bdev_io_split(void *_bdev_io) 
			 * size and then adjust to_next_boundary before starting the

			 * child I/O.

			 */

			assert(child_iovcnt == BDEV_IO_NUM_CHILD_IOV);

			to_last_block_bytes = to_next_boundary_bytes % blocklen;

			if (to_last_block_bytes != 0) {

				to_next_boundary_bytes += _to_next_boundary(to_next_boundary_bytes, blocklen);;

				uint32_t child_iovpos = child_iovcnt - 1;

				/* don't decrease child_iovcnt so the loop will naturally end */



				to_next_boundary_bytes += _to_next_boundary(to_next_boundary_bytes, blocklen);

				while (to_last_block_bytes > 0 && iovcnt > 0) {

					iov_len = spdk_min(to_last_block_bytes,

							   bdev_io->child_iov[child_iovcnt - 1].iov_len);

					bdev_io->child_iov[child_iovcnt - 1].iov_len -= iov_len;

					if (bdev_io->child_iov[child_iovcnt - 1].iov_len == 0) {

						child_iovcnt--;

							   bdev_io->child_iov[child_iovpos].iov_len);

					bdev_io->child_iov[child_iovpos].iov_len -= iov_len;

					if (bdev_io->child_iov[child_iovpos].iov_len == 0) {

						child_iovpos--;

						iovcnt--;

					}

					to_last_block_bytes -= iov_len;
@@ -1674,7 +1676,6 @@ _spdk_bdev_io_split(void *_bdev_io) 


				assert(to_last_block_bytes == 0);

			}

			child_iov_run_out = true;

			to_next_boundary -= to_next_boundary_bytes / blocklen;

		}
@@ -1699,10 +1700,6 @@ _spdk_bdev_io_split(void *_bdev_io) 
			remaining -= to_next_boundary;

			bdev_io->u.bdev.split_current_offset_blocks = current_offset;

			bdev_io->u.bdev.split_remaining_num_blocks = remaining;

			/* stop splitting until child_iov is available */

			if (spdk_unlikely(child_iov_run_out)) {

				return;

			}

		} else {

			bdev_io->u.bdev.split_outstanding--;

			if (rc == -ENOMEM) {